If you are familiar with Dahl's work he does use a lot of visual description to describe how nasty/nice/horrible a character is. He doesn't just use the word fat or ugly, he will used all manners of words in his visual descriptions and I'm sure he described the grandma's mouth like a 'puckered up dog's bottom' in GMM. Racist language has no place in children's books, however with old text, as others' have suggested it can be a starting point for discussion about the wrongs of the past.
I worry what we are doing to children by censoring things to the extreme. I am a woman and I would not have a problem reading 'formidable female.' Because in Dahl's book, Matilda, I know he would have written equally offensive remarks about some of the horrible male characters (namely Mr Wormwood.'
As a book loving little girl I adored Matilda. She was brave, smart, courageous and taught me to stick up for myself and others and carry on enjoying studying, reading and learning. I know I can't be the only girl that got inspired by that book.
In the Magic Finger, it taught me that people can be arseholes and shooting animals for pleasure isn't big or clever and not to let people bully you, because they believe they are better than you. I could go through most of his books, but I won't.
The positives in Dahl's books far outweighs the negatives. If he described one character as a formidable female, I'll get over it as he wrote so many fantastic, brave female characters. He was a champion of children being the hero's in all his stories and I love him for that.
Rant over.